Sister
I understnad how you feel. When you talk to the girls, make sure your aklaaq are of the highest degree, and befriend them, send them islamic emails etc.
Maybe you could organise a talk? You do the talking of course - and i have always found it very uplifting when you have a revert speak about the choices they have made. Maybe you could invite somebody over to speak, inshallah the girls will have mroe knowledge at the end.
Remember to give sallam to them even if you dont know them and smile and just be ...nice. If they're talking about something and it reminds you of a story from the time of the propeht (saw), tell them, kindly.